No I am pretty sure it doesn't, and if it did it wouldn't be noticable. The main reason is that with or without NAT, the PIX performs the same steps. It always checks the translation rules first (even with nat 0), then it checks the permissions (i.e. if there is an access-list and if the packet passes). The PIX ASA always checks translation rules first (and nat 0 is considered a translation as well to the PIX). Also, bear in mind the PIX is a specialized appliance designed for NAT and acls.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
[toc:faq]Introduction:This document describes details on how NAT-T
works.Background:ESP encrypts all critical information, encapsulating
the entire inner TCP/UDP datagram within an ESP header. ESP is an IP
protocol in the same sense that TCP and UDP are I...